Prof. Guy Lloyd-Jones of University of Edinburgh

Mechanisms, Molecules, Magnets

The presentation will focus on the general theme of in situ mechanistic analysis, illustrating the application of isotopes and kinetics in the elucidation of structure, reactivity, selectivity, and antagonism in reactions where speculation has become accepted mechanism through citation-reinforcement. The mechanisms of reactions used in organic synthesis should ideally be studied under the conditions in which they are applied (concentrations, solvent, temperature, etc.). In situ solution-phase NMR spectroscopy often proves ideal for this. It is nondestructive, is quantitative (with appropriate set-up) thus allowing determination of concentrations, is applicable to a wide range of nuclei common in organic and organometallic species. NMR also provides exquisite structural detail, is reasonably sensitive—particularly at the concentrations used in synthesis—and the instrumentation is routinely available in nearly every chemistry research department worldwide. However, features inherent in some reactions studied, including for example velocity, initiation, and homo/heterogeneity can affect the feasibility of collecting high-quality temporal concentration data using routine NMR spectrometers and probes. The need to find robust, versatile, and practical solutions to these issues have driven equipment and data-processing developments in the author's laboratory over the last decade. Reactions studied include the liberation, complexation-equilibria, and protolytic decomposition of a wide range of boron reagents and anion-initiated TMSCF₃-mediated processes. The presentation will draw on past, present, and unpublished work to highlight selected points.